GPR, or ground-penetrating RADAR (where RADAR is “RAdio Detection And Ranging), is a technology used to assess the composition and location of heterogeneous materials. GPR uses radio frequencies and is particularly useful in that it is both non-destructive and non-ionizing. In fact, GPR uses frequencies similar to a cellular phone, but at far lower power levels. Common applications include locating the precise position of rebar within a concrete wall/floor, identifying and locating buried objects underground, assessing the quality and uniformity of an asphalt or concrete highway surface, and detecting deterioration on bridge decks. In road surface applications, GPR is used, for example, to detect cracks, fissures, or contamination in any one of the chip seal, pavement layers, gravel base, and so forth. In many roadway applications, a resolution of features of the road surface of less than one inch (2.54 cm) is desired. Such systems may be mounted on vehicles traveling over the surface while acquiring measurement data. GPR systems are disclosed in more detail in U.S. Pat. No. 5,499,029 to Bashforth, et al., and U.S. Pat. No. 5,384,715 to Lytton, which are hereby incorporated by reference.
Ground Penetrating Radar (GPR) antennas are built in different sizes for different uses. Smaller antennas are generally higher in frequency, have higher resolution for displaying finer details, and are not able to penetrate as deep as lower frequency antennas. Larger antennas are generally lower in frequency, are able to penetrate deeper, but have a lower resolution, and so are not able to discriminate fine details. By performing a survey simultaneously with two antennas, a higher and a lower frequency model, the user is able to obtain the best quality of each antenna. The volume near the surface will have the best resolution, and the deeper volume will be viewed with the maximum range. Viewing the two separate pictures displayed can be difficult for the average user, even when viewed on the same monitor, as is the best practice currently known.
Further, alternating current carrying conductors (i.e., utility power lines) produce magnetic fields which can be detected with an transducer at proper frequencies. For detection of pipes, one can induce a signal onto the pipe or adjacent “tracer line” to aid in its detection. Typically, a magnetic field is detected from a power lines at 50 or 60 Hz, while the induced case uses higher frequency signals ranging from a few hundred Hz up to several hunded KHz. The magnetic field produced therefrom extends radially outwards from the direction of current flow. Examples of same include U.S. Pat. No. 8,742,747 to Pearson, U.S. Pat. No. 7,113,124 to Waite, and U.S. Pat. No. 8,188,745 to Overby, et al.
Each method of detection in the prior art has different drawbacks. Different types of interference affect the use of each one, causing false positive results or failing to locate the desired object. There is a need in the art to find better ways of detecting buried pipes, electrical lines, and other cables.